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A compression test determines behavior of materials under crushing loads. The
specimen is compressed and deformation at various loads is recorded.
Compressive stress and strain are calculated and plotted as a stress-strain
diagram which is used to determine elastic limit,
proportional limit, yield point,
yield strength and, for some materials,
Why Perform a Compression Test?
The ASM Handbook®, Volume 8, Mechanical Testing and Evaluation states: "Axial
compression testing is a useful procedure for measuring the plastic flow behavior and
ductile fracture limits of a material. Measuring the plastic flow behavior requires
frictionless (homogenous compression) test conditions, while measuring ductile
fracture limits takes advantage of the barrel formation and controlled stress and
strain conditions at the equator of the barreled surface when compression is carried out
with friction. Axial compression testing is also useful for measurement of elastic
and compressive fracture properties of brittle materials or low-ductility materials.
In any case, the use of specimens having large L/D ratios should be avoided to prevent
buckling and shearing modes of deformation1."
The image at right shows variation of the strains during a compression
test without friction (homogenous compression) and with progressively
higher levels of friction and decreasing aspect ratio L/D
(shown as h/d)1.
Modes of Deformation in Compression Testing
The figure to the right illustrates the modes of deformation in compression
testing. (a) Buckling, when L/D > 5. (b) Shearing, when L/D
> 2.5. (c) Double barreling, when L/D > 2.0 and friction is
present at the contact surfaces. (d) Barreling, when L/D < 2.0
and friction is present at the contact surfaces. (e) Homogenous
compression, when L/D < 2.0 and no friction is present at the
contact surfaces. (f) Compressive instability due to work-softening
The following materials are typically subjected to a compression test.
- Corrugated Cardboard
1ASM Handbook, Vol. 8, Mechanical Testing and Evaluation,
ASM International, Materials Park, OH 44073-0002, fig. 6(b), page 146; Test Methods,
first paragraph only, page 147; fig. 1, page 143; 2 sentences under Flexural Strength
Test, page 32.